The differences between Shader Model 4.1 and 5.0 are almost entirely on the side of ease of use for the programmer, with a secondary benefit for performance. You probably will never notice a visual difference.
As Tom's Hardware puts it in their look into Shader Model 5 (emphasis mine):
So the code is all in a single place, which makes bug correction easier. At the same time, legibility doesn’t suffer thanks to the organization of the code, which resembles the concept of virtual functions in object-oriented languages. This feature will be welcomed by programmers, but won’t have any real impact for gamers.
Essentially, programmers can now write more efficient code, with better organisation, and that brings fewer bugs, better testability, and consequently the possibility of (marginally) better performance. (Of course, if they still have to support SM 4.1, that may nullify the improvements in testability and fewer bugs, because they actually have to write more code, for each version of the Shader Model – but that's another story...)